Transfer half of the mixture to a greased 13x9-in. baking dish; sprinkle with half of the cheese. Top with remaining bread mixture. Separately cover and refrigerate strata and reserved prosciutto overnight.

Transfer half of the mixture to a greased 13x9-in. baking dish; sprinkle with half of the cheese. Top with remaining bread mixture. Separately cover and refrigerate strata and reserved prosciutto overnight.